Well, i received a prototype of a kit that used light instead of the other options to create a signal to make a MFB driver (Sander de Jong).
i used a regular woofer here since i am new to using in this case the circuit, a scope, and the camera to film it.... so i though lets start off with a regular ported woofer that i just plug off
(hopefully)
must be clear we had random results in what it does and if its usefull, depending on the type of panel.... so we are not sure. but for dynamic woofers it works for sure ! here a crude method and way of doing it.... by a newbie
i used a regular woofer here since i am new to using in this case the circuit, a scope, and the camera to film it.... so i though lets start off with a regular ported woofer that i just plug off
(hopefully)must be clear we had random results in what it does and if its usefull, depending on the type of panel.... so we are not sure. but for dynamic woofers it works for sure ! here a crude method and way of doing it.... by a newbie
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Btw @WrineX Do you aim for using very thin diaphragms on panels? I read in a planar headphone thread that weight of membrane is (relatively😊) irrelevant compared to the resistance of moving air. Also that weight and power of the etching/magnet field is much more important.
Good luck with MFB. I never heard motional feedback I think.
Cheers
Good luck with MFB. I never heard motional feedback I think.
Cheers
What delay is critical for covering frequencies of 20-100Hz?
I don’t understand, optical feedback does not see air pressure, which means that there is no way to suppress the standing wave of the room, etc. and so on.
well a mic pics up things without the woofer doing anything. so i guess it will create a feedback loop
when ever you thumb the ground by walking for instance
well i dont know if this all is practical
bu it is fun to play with. wanted to test it one some smaller panels. with different magnet motor. my guess its not worth all the effort. but we will seeIf the transformer is well executed, what is the point? ESLs are probably the most linear drivers you can get. And the transformer will probably introduce additional delay, further limiting the frequency range for feedback.
The thing I have been ruminating is whether it would be possible to use a voltage divider from the transformer output for feedback to the amplifier in order to overcome transformer nonlinearity (if this is a problem at all). Again delay from the transformer and the fact that its output is capacitively loaded might make obtaining stability impossible.
What else is possible? Extra secondary for feedback - maybe? Current driving the primary - probably not!
The thing I have been ruminating is whether it would be possible to use a voltage divider from the transformer output for feedback to the amplifier in order to overcome transformer nonlinearity (if this is a problem at all). Again delay from the transformer and the fact that its output is capacitively loaded might make obtaining stability impossible.
What else is possible? Extra secondary for feedback - maybe? Current driving the primary - probably not!
well i would not use this feedback for an ESL i just wondered what you can do with a planar magnetic. even then i doubt if its usefull enough for the extra money spend. but that wont hold me from playing with it and see what it could be used for. i mean it can always be used for norrnal dynamic driver in the end
i just wondered what you can do with a planar magnetic. even then i doubt if its usefull enough for the extra money spend. but that wont hold me from playing with it and see what it could be used for. i mean it can always be used for norrnal dynamic driver in the end Thanks for the clarification. The thought of planar magnetic drivers did not enter my mind when reading this thread.
Again, push-pull magnetostats (e.g. B&G) tend to be fairly linear, and they are not LF drivers, so not where MFB works well. You don't have the transformers to deal with, though.
B&Gs have hardly a resonance frequency, so I would expect them to benefit from current drive. That is easier to implement and also across the whole frequency band.
Again, push-pull magnetostats (e.g. B&G) tend to be fairly linear, and they are not LF drivers, so not where MFB works well. You don't have the transformers to deal with, though.
B&Gs have hardly a resonance frequency, so I would expect them to benefit from current drive. That is easier to implement and also across the whole frequency band.
Well when you go lower resonance becomes... well more prominent. anyhow its just something cool to play with. as i said... it might not at all outweigh the costs etc. could make a bigger panel for the extra money but it might be interesting for smaller width panel that can play low.... at the cost of power and remove resonance to a extend.
but it might be interesting for smaller width panel that can play low.... at the cost of power and remove resonance to a extend.
I once tried this with ESL's. But glueing a mic that produces mV of signal against a stator with several kV swing made me run into some serious crosstalk issues. Same mic output with and without bias on the esl
I don't think any amount of shielding will reduce the crosstalk enough to make the mic output usable.
However with magnetic planars, it could work I guess. Picking up ambient noises is not a problem as long as you can achieve sufficient S/N ratios, with the mic so close to the membrame that should be feasible.
Another option would be to isolate a section of the membrame in a magnetic planars and use that to create a small capacitor with one of the stators. That can be used to produce an accurate feedback signal with some simple electronics.
I don't think any amount of shielding will reduce the crosstalk enough to make the mic output usable.
However with magnetic planars, it could work I guess. Picking up ambient noises is not a problem as long as you can achieve sufficient S/N ratios, with the mic so close to the membrame that should be feasible.
Another option would be to isolate a section of the membrame in a magnetic planars and use that to create a small capacitor with one of the stators. That can be used to produce an accurate feedback signal with some simple electronics.
First test on the rubber magnet planar magnetic panel, i did use more damping then normal. i think these kind of panels dont have enough control to remove res completely brown without the MFB green with well it extends lower and shifts the resonance. then i end up with having trouble with excursion though so high excursion (instead of rubber magnet with 1mm excursion) would work better i think. another thing i noticed having more tension on the foil makes it better to but will raise resonance in frequency. aah well maybe i refoil them one day measure rather close 50 cm +- since where the speakers are standing wont allow low frequencies below 60 Hz all that much.. i had to move them to the other corner if i wanted...
brown without the MFB green with well it extends lower and shifts the resonance. then i end up with having trouble with excursion though so high excursion (instead of rubber magnet with 1mm excursion) would work better i think. another thing i noticed having more tension on the foil makes it better to but will raise resonance in frequency. aah well maybe i refoil them one day measure rather close 50 cm +- since where the speakers are standing wont allow low frequencies below 60 Hz all that much.. i had to move them to the other corner if i wanted...
Well its hard to tell, i am not convinced it removes much distortion , it might from the resonance but maybe purely because it has less output (less excursion). the added frequency response is a bit harder to compare.... since you are forcing it. and there was much less output at 35hz before... so the distortion that was already there will be even more... im still thinking about trying to EQ it so it looks the same then compare them ? just an idea